Process for the production of ferromanganese from high-grade manganese-bearing materials



Aprll 15, 1958 M. J. UDY 2,830,889

. PROCESS FOR THE PRODUCTION OF FERROMANGANESE FROM HIGH-GRADEMANGANESE-BEARING MATERIALS Filed July 22, 1955 High Grade ManganeseOxide Ore or Concentrates Kiln 900 C. l200C. Calcine to constantComposition Elimination of CO H 0, 0 etc.

Iron Scrap Calcium Oxide Dry Electrlc Furnace Coke (Covered) L .\3ooc.-l500 c.

Fe MnC Stag Waste (C06 (5%77 C) Ca0+ Mg0+ 800,

6112.10 Sioz= 2 INVENTOR 8 Marvin J. Udy M 6M ATT NEY United StatesPatent PRQQESS FDR THE PRODUCTION OF FERRO- MANGANESE FROM HIGH-GRADEMANGA- NESE BEARING MATERIALS Marvin I. Udy, Niagara Falls, N. Y.,assignor to Strategic Udy Metallurgical & Chemical Processes Limited,Hamilton, Ontario, Canada, a corporation of Ontario Application July 22,1955, Serial No. 523,696.

2 Claims. (Cl. 75-11) The present invention relates to metallurgy andhas for an object the provision of an improved metallurgical process.More particularly, the invention contemplates the provision of animproved metallurgical process for the recovery of manganese frommanganese-bearing ,materials. The principal object of the invention isthe provision of an improved single stage reduction process for theproduction of ferromanganese from relatively highgrade manganese-bearingmaterials containing manganese in oxide form.

This application is a continuation-in-part of my copending United Statesapplication, Serial No. 341,415, filed March 10, 1953, and entitledManganese Recovery, which was issued as U. S. Patent No. 2,775,518 onDecember 25, 1956.

According to some heretofore customary practices employed in thesmelting of manganese oxide-bearing materials with solid carbon,substantial quantities of basic iluxing materials such as lime anddolomite are employed for fluxing acid components of the charge, such assilica. This type of practice results in the production of largequantities or volumes of high-melting point slags which, in turn,necessitate operating at relatively high temperatures in order toproduce fluid or workable slags. The use of high temperatures results inhigh volatilization losses of manganese, and, in addition, theproduction of large quantities or volumes of slag contributes further toloss of manganese values by providing large volumes of solvent orvehicle for manganese compounds from which it is impossible to recovermanganese on any economical basis.

Furthermore, in prior processes of the general-class described, theconventional practice is to effect reduction of the manganese ore in asubmerged arc type of electric furnace to which charge material is fedsuch as to build up and maintain a substantially deep bed or column ofraw charge material surrounding the furnace electrodes. In this type ofoperation, it is not possible to obtain more than approximately eightypercent (80%) of the manganese values contained in the original chargematerial, even when treating high-grade manganese oxide ores, exceptpossibly by resorting to multi-stage reduction techniques wherein themanganese-bearing slag product recovered from an initial reductionoperation is treated in a subsequent stage or stages for furtherrecovery of manganese or manganese-bearing products in the mannerdescribed in my aforementioned patent. Under existing operatingtechniques, attempts at increasing the percentage recovcry in theinitial reduction stage usually result in overdriving the furnace withsubsequent loss of manganese through volatilization.

in accordance with a preferred process of the present invention, I amable to effect consistent recoveries in the order of ninety percent(90%) and higher in a single stage reduction operation employing naturalor altered charge material of relatively low iron content and relativelyhigh manganese (oxide) content by smelting in a ice covered electricfurnace under accurate conditions of temperature control, a pre-treated,substantially constant composition manganese oxide-containing chargewith a controlled amount of carbonaceous reducing material, andcontrolled amounts of fluxing material and added iron, where required,to effect reduction to the metallic state of manganese oxide of thecharge with the direct production of standard grade high-carbon (5 to 7%C) ferromanganese Mn), and a waste slag product.

The invention is based in part on my discovery that substantialadvantages with respect to manganese recovery may be obtained byavoiding the addition of substantial amounts of basic fiuxing materialto a charge of manganese oxide-bearing material which isto be smelted inthe presence of a solid carbonaceous reducing agent such as coal orcoke. In accordance with one feature of my invention, a high-grademanganese oxide-bearing ore, concentrate, or the like, in which themanganese is present in the form of one or more higher oxides thanmanganese oxide (MnO), as, for example, in theform of manganese dioxideor pyrolusite (MnO or hausmannite (Mn O or both, is heated in a rotarykiln or other suitable equipment, to remove all water, the labile oxygenfrom MnO CO S, etc., thereby to stabilize the ore or concentrate to aconstant composition with respect to oxygen content in order to providebetter control of reduction by carbon of the coke, coal, etc. Unlike thetwo stage process of my copending application, in accordance with aprocess of the present invention, I add to the furnace charge calciumoxide (CaO) or similar basic fluxing material, such as magnesium oxide(MgO), to provide with silica present in the charge, slag having abase-acid ratio of 2 base to 1 acid. The heated and stabilized productor charge is then fed without substantial dissipation of heat, with drycarbon in the form of coke, coal, wood or charcoal, into a coveredelectric furnace and smelted according to the principles disclosed in myaforementioned patent, as described more fully hereinafter.

In the submerged arc type of smelting technique heretofore employed inindustry, the positioning of charge material surrounding the furnaceelectrodes in the manner described hereinbefore, causes an undesirableconcentration of coke adjacent the electrodes which makes it virtuallyimpossible to control operating temperatures within the furnace to anyaccurate degree, and very often results in over-reduction of the chargewith increased volatilization losses. In accordance with a furtherfeature of the present invention, I avoid this phenomenon completely andam able to attain a very accurate temperature control through carefulpositioning of the furnace electrodes in a manner similar to thatdescribed in my aforementioned copending application. Specifically, in asingle stage reduction operation for the production of ferromanganesefrom high-grade manganese oxide-bearing materials, I prefer to employ acovered electric furnace provided with one or more verticallyextendingelectrodes mounted in conventional form. In operating such afurnace according to a process of the present invention, I avoid wettingof the electrodes with molten slag and thereby avoid full slagresistance heating by maintaining their arcing tips a distance rangingfrom about one-half inch /2") above the surface of molten slag in thefurnace to about three inches (3") below the surface of the molten slag.By operating the furnace in this manner, the heat generated in the slagby the IR effects due to the resistance of the slag will reach asubstantially constant temperature equivalent to the melting point ofthe slag and no higher while there is unmelted charge within thefurnace. On

slag bath as well as the rate of feed of charge material (lbs. perkw.-hr.) to the furnace, I am able to regulate and control the combinedslag resistance and are resistance heating to temperatures within 100 C.of the melting point of the alloy produced. Furthermore, I avoidpenetration of the electrodes within a descending column of raw chargeby introducing charge material into the interior of the arcresistance-slag resistance furnace and onto the surface of a molten slagbath maintained therein at a rate such that it is deposited on thesurface of the molten slag bath between the furnace walls and theelectrodes, or at a rate and direction of flow such that it does notflow into contact with the electrodes and builds up on the surface ofthe slag to a maximum depth of only a few inches, if at all. I havefound that under such conditions of operation vaporization of manganeseis substantially completely avoided.

In carrying out a process of the invention, a further important featurethereof resides in the preliminary treatment of manganese oxide ore forpurposes of providing a reduction charge of substantially constantcomposition. Thus, I have found that it is essential for proper carbondetermination and subsequent reduction in the smelting stage, that themanganese-bearing material be stabilized to a substantially constantcomposition by removal of water, carbon dioxide, oxygen of manganesedioxide, etc. For this purpose, I calcine raw manganese oxide-bearingore prior to the single stage reduction by heating the ore in a rotarykiln or similar piece of equipment at a temperature within the range 900C. to 1200 C.

The aforementioned and other features and objects of the invention maybe best understood by reference to the following description of specificembodiments thereof taken in conjunction with the accompanying drawingwherein:

Fig. l is a sectional elevational view of a covered electric furnaceillustrating the single stage reduction technique employed in effectinga process of my invention; and

Fig. 2 is a fiow diagram illustrating the exact sequence of stepsinvolved in a preferred process of the present invention.

In carrying out a process of the invention for smelting a chargecomprising manganese oxide-bearing ore or concentrates, the smeltingcharge employed may consist essentially of the manganese oxide-bearingmaterial, added basic fluxing material, as required, solid carbonaceousreducing material, such as coal or coke, and added iron, preferably inthe form of scrap iron in an amount sufficient to provide for theproduction of standard grade (80%) fen'omanganese. The components of thecharge are so proportioned as to provide carbonaceous reducing agent inamount sufficient to reduce to the metallic state iron of iron oxidethat may be present in the charge,

and to reduce to elemental manganese the higher oxides of manganesepresent in the charge. Thus, in calculating a charge for the singlestage smelting of a high grade ore or concentrate which has beenstabilized by calcining the raw ore or concentrate in the mannerexplained above, I calculate all basic constituents other than manganeseoxide, such as calcium oxide, magnesium oxide, barium oxide, etc., tothe equivalency of calcium oxide, and adjust the equivalent calciumoxide to the silica in the ore or concentrate to provide a slag of 2base to 1 acid (or anywhere within the range 1.7 to 2.2 base to 1 acid),i. e., MgO-l-BaO-i-CaO, etc. to SiO should be in the ratio of about 2:1;calcium oxide or an equivalent added basic fiuxing agent being addedonly as required to adjust the base-acid ratio to the desired range.Alumina (A1 when present in the ore or concentrates in amounts less thanten to twelve percent (-12%) may be disregarded in the calculations.Larger amounts of alumina are calculated to Si0 equivalency. It is ofthe utmost importance for efiicient reduction in the smelting stage,that the carbon determination be made on the basis of a'substantiallyconstant composition charge, and, accordingly, that feature of myinvention involving stabilization of the charge material by calcining,contributes substantially to the overall efiiciency of the process. Itis essential that the coal, coke, etc., used for reduction be dry, and,that carbon be provided in an amount sufficient for reduction ofmanganese and iron oxides, chemical combination with iron and manganesefor the production of highcarbon ferromanganese, and to form in thebasic slag (2CaO to lSiO a small amount of calcium carbide (CaC It isthe formation and presence in the slag of but a trace of calcium carbidewhich permits the production of slags very low in manganese, in that, aslight amount of calcium carbide in the slag upsets the equilibrium ofthe manganese oxide and slag and permits almost complete reduction ofmanganese. In this manner, slags containing one percent (1%) or less ofmanganese can be produced readily as compared with ten percent (10%) totwenty percent (20%) present in slags formed in accordance withconventional smelting techniques. Alternatively, instead of forming thecalcium carbide in the slag from the lime and coke additions, I may addcalcium carbide to the charge directly in varying quantities either inthe form of a high-grade product (4.75 cu.

ft. C H per pound) or a low grade product (2.5 to 3.5 cu. ft. C H perpound). The calcium carbide may be used in whole or in part with coke orin place of coke as the reducing agent. It functions to supply lime forthe silica and acts as a reducing agent for manganese and iron when usedin larger amounts than the trace neces sary for producing very lowmanganese slags. I may also employ a noncarbonaceous reducing agent suchas ferrosilicon, silicon carbide or aluminum to reduce last traces ofmanganese from manganese slags to produce waste slags very low inmanganese in lieu of calcium carbide in the manner explained above,provided lime is added, as required, to maintain the desired ratio of2.0 base to 1.0 acid within the slag.

In smelting a charge in accordance with the single stage reductiontechnique of my invention, I employ a covered electric arc furnaceprovided with one or more vertically extending electrodes, and I operatethe furnace at a voltage so as to maintain the arcing tips of the one ormore electrodes in position with respect to molten slag contained in thefurnace within about one-half inch /2") above the surface of the moltenslag bath to about three inches (3") below the surface of the slag bath,thereby avoiding wetting or immersion of the electrodes by the slag.Furthermore, I introduce charge material into the furnace and onto thesurface of the molten slag bath therein in such manner as to avoid anysubstantial buildup of charge material around the electrodes. Byoperating the furnace in this manner, I am able to maintain a veryaccurate temperature control within the furnace, which, for thetemperature of the slags utilized in accordance with the invention, maybe within the range 1300 C. to 1500" C., thereby substantially avoidingvaporization of manganese as characteristically occurs in conventionalsubmerged types of smelting operations by reason of the hightemperatures produced by accumulation of coke, etc. Furthermore, byregulating the electrodes in this manner, I am able to insure deliveryto the molten slag bath of substantially all of the arc-developed heatand can inhibit any substantial dissipation of heat due to reflection. Ialso effectively avoid the establishment of high pressure zones aroundthe electrodes caused by carbon dioxide gases generated during thereduction process becoming entrapped by deep beds of raw chargematerial, as occurs in conventional submerged arc operations, and theattendant danger to operators resulting from periodic so-called blowingunder action of gases entrapped in this manner.

The exact method of operating a furnace in accordance with my invention.may be best understood by reference to Fig. 1 of the drawing wherein Ihave shown an arc electric furnace 10 whichmay be of anysuitableconfiguration in horizontal cross-section. The furnace 10 comprises ahearth or bottom portion 11, side walls 12, and a roof 13 all formed ofappropriate refractory materials (preferably carbon-lined) The furnaceroof 13 is providedwith suitable openings through which electrodes 14(one shown) extend and which permit vertical movement of the electrodesin accordance with operational demands and characteristics. The spacebetween the electrodes and the edge of the openings through which theyextend or project may be provided with any suitable packing or sealingmeans to -inhibit or restrict the flow of gases between the interior andthe exterior of the furnace without interfering with the necessaryvertical movement of the electrodes.

Hoppers 15 having their lower portions extending through and sealed inopenings in the roof 13 are provided adjacent the outer side edges ofthe are electric furnace 10 in alinement with the electrodes to permitintroduction of charge materials 16 into the interior of the furnace.Those portions of the side walls of the furnace immediately beneathhoppers 15, as indicated by reference numeral 17 in Fig. 1, preferablyare so designed as to provide a slope corresponding to or equivalent tothe angle of repose of the charge material. Pref erably, the slopedportions of the walls are stepped, as shown in Fig. 1, to provide forthe deposition and retention thereon of protective coatings of chargematerial. A conduit (not shown) may be provided for communieating withthe interior of the furnace 10 through an opening in the roof to permitthe collection andutilization of carbon monoxide produced during thecourse of the process. A charging spout or runner or launder 18 isprovided to permit the introduction of molten charge material into theinterior of the furnace 10 when the furnace is employed in multi-stageoperations such as those described in my aforementioned patent, andwhich may be employed in accordance with a process of the presentinvention, if desired, for introducing hot calcined ore or concentratesinto the furnace. Alternatively, the ore or concentrates after calciningto a constant composition may be introduced into the interior of thefurnace 10 as a component of the charge material supplied throughhoppers 15 including carbonaceous reducing material, and added basicfiuxing material and iron, as required. The furnace 10 is furtherprovided with a conventional taphole 19 through which moltenferromanganese and molten slag may be delivered from the interior of thefurnace to a suitable ladle 20 at appropriate times.

In order to initiate operation of the furnace I may deliberately addextra slag of approximately a 2:1 ratio of CaO to SiO to establish ashallow layer of molten slag within the furnace. After the slag hasaccumulated, it is removed as required, but I always leave sufiicient:slag in the furnace so that the electrode tips can be carried on theslag to the depth desired, as specified hereinbefore. II have found thatoperation with the electrodes carried to a depth of 'one-half inch /2")above the surface of molten slag to a maximum of three inches (3")within the shallow layer of molten slag produces optimum results underactual operating conditions. Operation of the furnace in this mannerpermits the conjoint use of :arc resistance and slag resistance heatingwithinthe smelting furnace and the total overall power requirements orpower consumption is of the order of about twenty-four hundred kilowatthours (24-00 kw.-hr.) per ton of standard grade ferromanganese producedwhich represents a saving of about thirty percent of the power usuallyrequired for carrying out electric furnace processes of the typeemployed heretofore. Through operation of the furnace constantly as anarc resistance-slag resistance furnace with short arcs, and, by reasonof the substantially constant resistance slag bath obtainedv throughcontrol of the depth of slag, I am able to operate at higher voltages:and a constant power factor of 95% as compared with power factors of75% to 85% at which large are electric furnaces are operated inaccordance with heretofore customary practices.

In the operation of the electric furnace according to my invention,automatic electrode regulators are set to maintain the electrodes inconstant or substantially fixed positions relative to the surface of themolten slag bath, because, for a particular type of operation, the slagis of substantially constant resistance. When an increase or decrease inthe temperature of the molten slag is desired for a particularoperation, the voltage and power input is simply increased or decreasedand the electrode regulator is adjusted to maintain the arc lengthsWithin the desired range specified hereinbefore. In following thisprocedure the resistance is maintained constant and, consequently, thepower input is increased or decreased.

It should be apparent that by increasing or decreasing the arc gapswithin the limits specified hereinbefore, I am able to control both areresistance heat supplied to the charge and slag resistance heatdeveloped within the charge, and the conjoint use of heat supplied fromboth sources enables me to effect a very accurate temperature control ofthe overall slag bath. Furthermore, the temperature control effected inthis manner is not subject to frequent unbalance because of localintense temperature zones caused by coke accumulations, etc., since Iavoid the buildup of charge material around the electrodes and therebyefie'ctively avoid conditions which lead to the establishment of suchzones of uncontrollable heat. While I prefer to employ a covered furnacein the process of my inpention, a furnace without a cover may be usedalthough not without some sacrifice in efficiency.

When the ore or concentrate is defincient in iron, iron in metallic formor in the form of iron oxide may be incorportaed in a charge comprisingthe ore or concentrate in an amount sufiicient to provide for theproduction of standard grade ferromanganese. In actual practice, Iprefer to use iron in the form of scrap iron or steel for this purpose.

The following is an analysis of typical ore used in the production offerromanganese in accordance with a process of the invention.

Manganese oxide are (high grade) Percent Manganese (Mn) 48.00 Calculatedto MnO 76.00 Calculated to M11 0 66.50 Ferric oxide (Fe O 1.20 Alumina(A1 0 1.20 Barium oxide (E210) 2.20 Calcium oxide (CaO) 5.40 Magnesiumoxide (MgO) 1.09 Silica (Slo 6.50 Phosphorus (P) 0.03

The following example illustrates the specific application of theforegoing principles and objects to the production of ferromanganese ina single stage reduction operation of the invention as illustrated inthe flow diagram of Fig. 2:

EXAMPLE A charge consisting essentially of 1000 pounds of highgrademanganese ore of approximately the composition indicated above, 296.7pounds of coke fixed carbon), 44.0 pounds of calcium oxide, and 10.0pounds of iron is fed to a rotary kiln or other sintering device andheated with oil, gas or coal to a temperature of 1100 C. I may add thereducing agent (coke) to the charge to the kiln or to the electricfurnace and may also employ lime in the form of limestone within thekiln charge. The hot charge from the kiln may be cooled and used in acold state if desired and economics warrant such practice.

In practice, coke may be added to plus or minus ten percent (210%) andis varied from time to-time and adjusted for carbon entering the bath byreason of electrode consumption. With the ore stabilized to Mn O orMnSiO or combined with lime and silica, the proper variation of coke iseasily established. Excess coke is provided to form a small amount ofcalcium carbide unless the calcium carbide is added directly to thecharge as explained hereinbefore.

The hot product discharged from the kiln is fed directly to the electricfurnace of the type illustrated in Fig. 1, and smelted at a temperaturewithin the range 1300" C. to 1500 C. to reduce the iron and manganeseoxides with the production of feromanganese of 80% manganese, 7% carbon,and a waste slag product containing calcium carbide and manganese in theorder of a trace to one percent (1.0%). Volatilization losses are of theorder of one to two percent (12%) of the manganese, and recoveries ofmanganese in the form of ferromanganese are of the order of ninety-fiveto ninetyseven percent (9597%).

In alternative processes of the invention, non-carbonaceous reducingagents such, for example, as silicon, aluminum and magnesium as such orin the "form of low-carbon alloys may be employed as reducing agents inthe treatment of ore or concentrates to provide for or permit theproduction of low-carbon and mediumcarbon grades of ferromanganese, asdistinguished from high-carbon products formed or produced whencarbonaceous reducing agents are employed.

Since it is considered obvious that many changes and modifications canbe made in the foregoing methods and procedures without departing fromthe nature and spirit of my invention, it is to he understood that theinvention is not to be limited to the specific details offered by way ofillustration above, except as set forth in the following claims.

I claim:

1. A single stage smelting process for producing ferromanganese fromrelatively high-grade manganesebearing material comprising oxides ofmanganese, iron, calcium and silica, that comprises calcining themanganese-bearing material at a temperature controlled within the range900-1200" C. to stabilize the same by elimination of water and labileoxygen with the production of a substantially constant compositionreduction burden; passing the hot stabilized charge thus produceddirectly into a covered open-arc electric furnace and onto the surfaceof a molten slag bath maintained therein in the presence of (l) reducingmaterial in an amount sufficient to eitect reduction of the iron andmanganese oxides of the material to the metallic state, (2) addedcalcium oxide in an amount sufiicient to provide for the production ofresidual slag comprising silica and basic oxides in proportions equal toabout two molecules or" basic oxide to each molecule of silica, and (3)iron in an amount as required to combine with manganese and ironnaturally present in the material to produce a desired grade offerromanganese; smelting the charge at a temperature controlled Withinthe range 1300-1500 C. to eifect reduction to the metallic state of theiron and substantially all of the manganese oxide of the material bymeans of said reducing material with the production of a moltenferromanganese product and molten residual slag low in iron andmanganese; and separating and recovering the ferromanganese from theresidual slag; said smelting temperature being controlled within therange 1300-1500 C. during the course of the process and vaporization ofmanganese being minimized by (1) maintaining the arcing tips of thefurnace electrodes between about one-half inch /2") from the uppersurface of the molten slag bath therein and about three inches (3) belowthe upper surfacev of said molten slag bath, (2) maintaining asubstantially constant resistance slag bath Within the furnace bycontrolling the depth of molten slag, and (3) introducing chargematerial into the furnace and onto the surface of the molten slag baththerein at a rate and in a direction controlled to avoid substantialsubmergence of the arcing tips of the electrodes within raw chargematerial.

2. A single stage smelting process for producing forromanganese fromrelatively high-grade manganese-bearing material comprising oxides ofmanganese, iron, calcium and silica, that comprises calcining themanganesebearing material at a temperature controlled within the range900-1200 C. to stabilize the same by elimination of water and labileoxygen with the production of a substantially constant compositionreduction burden; passing the hot stabilized charge thus produceddirectly into a covered open-arc electric furnace and onto the surfaceof a molten slag bath maintained therein in the presence of 1) solidcarbonaceous reducing material in an amount sufiicient to eifectreduction of the iron and manganese oxides of the material to themetallic state, to provide for chemical combination with metallic ironand manganese in the production of a high-carbon ferromanganese product,and to form with calcium oxide at least a trace amount of calciumcarbide within the residual slag, (2) added calcium oxide in an amountsufficient to provide for the production of residual slag comprisingsilica and basic oxides in proportions equal to about two molecules ofbasic oxide to each molecule of silica, and (3) iron in an amount asrequired to combine with manganese and iron naturally present in thematerial to produce a desired grade of ferromanganese; smelting thecharge at a temperature controlled within the range 1300-1500 C. toeffect reduction to the metallic state of the iron and substantially allof the manganese oxide of the material by means of said solidcarbonaceous re ducing material with the production of a moltenhighcarbon ferromanganese product and molten residual slag low in ironand manganese and comprising silica, basic oxides and at least a traceamount of calcium carbide; and separating and recovering theferromanganese from the residual slag; said smelting temperature beingcontrolled within the range 1300-1500 C. during the course of theprocess and vaporization of manganese being minimized by (1) maintainingthe arcing tips of the furnace electrodes between about one-half inch/2) from the upper surface of the molten slag bath therein and aboutthree inches (3") below the upper surface of said molten slag bath, (2)maintaining a substantially constant resistance slag bath within thefurnace by controlling the depth of molten slag, and (3) introducingcharge material into the furnace and onto the surface of the molten slagbath therein at a rate and in a direction controlled to avoidsubstantial submergence of the arcing tips of the electrodes within rawcharge material.

References Cited in the file of this patent UNITED STATES PATENTS

1. A SINGLE STAGE SMELTING PROCESS FOR PRODUCING FERROMANGANESE FROMRELATIVELY HIGH-GRADE MANGANESEBEARING MATERIAL COMPRISING OXIDES OFMANGANESE, IRON, CALCIUM AND SILICA, THAT COMPRISES CALCINING THEMANGANESE-BEARING MATERIAL AT A TEMPERATURE CONTROLLED WITHIN THE RANGE900-1200*C. TO STABILIZE THE SAME BY ELIMINATION OF WATER AND LABILEOXYGEN WITH THE PRODUCTION OF A SUBSTANTIALLY CONSTANT COMPOSITIONREDUCTION BURDEN, PASSING THE HOT STABILIZED CHARGE THUS PRODUCEDDIRECTLY INTO A COVERED OPEN-ARC ELECTRIC FURNACE AND ONTO THE SURFACEOF A MOLTEN SLAG BATH MAINTAINED THEREIN IN THE PRESENCE OF (1) REDUCINGMATERIAL IN AN AMOUNT SUFFICIENT TO EFFECT REDUCTION OF THE IRON ANDMANGANESE OXIDES OF THE MATERIAL TO THE METALLIC STATE, (2) ADDEDCALCIUM OXIDE IN AN AMOUNT SUFFICIENT TO PROVIDE FOR THE PRODUCTION OFRESIDUAL SLAG COMPRISING SILICA AND BASIC OXIDES IN PROPORTIONS EQUAL TOABOUT TWO MOLECULES OF BASIC OXIDE TO EACH MOLECULE OF SILICA, AND (3)IRON IN AN AMOUNT AS REQUIRED TO COMBINE WITH MANGANESE AND IRONNATURALLY PRESENT IN THE MATERIAL TO PRODUCE A DESIRED GRADE OFFERROMANGANESE, SMELTING THE CHARGE AT A TEMPERATURE CONTROLLED WITHINTHE RANGE 1300-1500* C. TO EFFECT REDUCTION TO THE METALLIC STATE OF THEIRON AND SUBSTANTIALLY ALL OF THE MANGANESE OXIDE OF THE MATERIAL BYMEANS OF SAID REDUCING MATERIAL WITH THE PRODUCTION OF A MOLTENFERROMANGANESE PRODUCT AND MOLTEN RESIDUAL SLAG LOW IN IRON ANDMANGANESE; AND SEPARATING AND RECOVERING THE FERROMANGANESE FROM THERESIDUAL SLAG; SAID SMELTING TEMPERATURE BEING CONTROLLED WITHIN THERANGE 1300-1500*C. DURING THE COURSE OF THE PROCESS AND VAPORIZATION OFMANGANESE BEING MINIMIZED BY (1) MAINTAINING THE ARCING TIPS OF THEFURNACE ELECTRODES BETWEEN ABOUT ONE-HALF INCH (1/2") FROM THE UPPERSURFACE OF THE MOLTEN SLAG BATH THERIN AND ABOUT THREE INCHES (3") BELOWTHE UPPER SURFACE OF SAID MOLTEN SLAG BATH, (2) MAINTAINING ASUBSTANTIALLY CONSTANT RESISTANCE SLAG BATH WITHIN THE FURNACE BYCONTROLLING THE DEPTH OF MOLTEN SLAG, AND (3) INTRODUCING CHARGEMATERIAL INTO THE FURNACE AND ONTO THE SURFACE OF THE MOLTEN SLAG BATHTHEREIN AT A RATE AND IN A DIRECTION CONTROLLED TO AVOID SUBSTANTIALSUBMERGENCE OF THE ARCING TIPS OF THE ELECTRODES WITHIN RAW CHARGEMATERIAL.